Shell (computing)

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In computing, a shell is a piece of software that provides an interface for users. Typically, the term refers to an operating system shell which provides access to the services of a kernel. However, the term is also applied very loosely to applications and may include any software that is "built around" a particular component, such as web browsers and email clients that are "shells" for HTML rendering engines. The name 'shell' originates from shells being an outer layer of interface between the user and the innards of the operating system (the kernel).

Operating system shells generally fall into one of two categories: command line and graphical. Command line shells provide a command line interface (CLI) to the operating system, while graphical shells provide a graphical user interface (GUI). In either category the primary purpose of the shell is to invoke or "launch" another program; however, shells frequently have additional capabilities such as viewing the contents of directories.

The relative merits of CLI- and GUI-based shells are often debated. CLI proponents claim that certain operations can be performed much faster under CLI shells than under GUI shells (such as moving files, for example). However, GUI proponents advocate the comparative usability and simplicity of GUI shells. The best choice is often determined by the way in which a computer will be used. On a server mainly used for data transfers and processing with expert administration, a CLI is likely to be the best choice. On the other hand, a GUI would be more appropriate for a computer to be used for image or video editing and the development of the above data.

Contents 1 Text (CLI) shells 1.1 Unix shells 1.2 Non-Unix shells 1.3 Shells for programming languages 2 Graphical (GUI) shells 2.1 On Microsoft Windows 2.2 On the X Window System 2.3 On other platforms 3 See also

[edit] Text (CLI) shells

[edit] Unix shells

Notable historic or popular Unix shells include:

• Bourne shell (sh)
  • Almquist shell (ash)
    • Debian Almquist shell (dash)
  • Bourne-Again shell (bash)
  • Friendly interactive shell (fish)
  • Korn shell (ksh)
• C shell (csh)
  • TENEX C shell (tcsh)
• Es shell (es)
• esh (Unix) – Easy Shell
• rc shell (rc) – shell for Plan 9 and Unix
• runscript – The initial shell interpreter used to process startup scripts in Gentoo
• scsh (Scheme Shell)
• Stand-alone Shell (sash)
• Z shell (zsh)

[edit] Non-Unix shells

• 4DOS, 4OS2, 4NT – shells for DOS, OS/2, and Windows NT written and sold by JP Software. The Take Command programs were compatible shells requiring and enjoying a GUI.
• Amiga CLI/Amiga Shell which f